This application claims priority to Japanese Patent Application No. 2001-174462 filed Jun. 8, 2001, which application is herein expressly incorporated by reference.
1. Field of the Invention
The present invention relates to a construction that prevents water from penetrating between electric wires inserted into a grommet. More particularly, the present invention improves water penetration prevention between electric wires of a wire harness, inserted into the grommet. Generally, the wire harness is installed in a through-hole of a panel or the like of a vehicle body.
2. Background of the Invention
In vehicles, a rubber grommet is used to waterproof the through-hole of a partitioning wall when a wire harness is passed through the through-hole. A plurality of electric wires which constitute the wire harness are inserted into the grommet. There is a fear that water penetration may occur due to the difference between the atmospheric pressure of an engine compartment and the interior of the vehicle.
Japanese Patent Application Laid-Open No. 2000-165061 discloses a construction to prevent water from penetrating between electric wires which are to be inserted into a grommet. FIGS. 5A and 5B, illustrate a construction to prevent water from penetrating between electric wires. The electric wires W of the wire harness are rolled to be inserted into the electric wire insertion portion 2 of the grommet 1. The electric wires W are disposed at required intervals and sandwiched between the foamed sheets 3. Thereafter, the electric wires W are inserted into the electric wire insertion portion 2. During this step the electric wires W are compressed. Thus, the electric wires W are independently surrounded by the foamed sheet 3. Since gaps do not occur between the electric wires W, it is possible to prevent water from penetrating through the gaps between the electric wires W.
In the above-described water penetration prevention construction, the electric wires W are sandwiched between the foamed sheet 3. An adhesive is applied to one of the sheets and the electric wires W are sandwiched between the upper and lower foamed sheets 3. Thereafter the electric wires W are rolled. The surface of the foamed sheet 3 without the adhesive is rough. Thus, it is possible that when the foamed sheet 3 is rolled and the rough surface contacts itself, depending on the compressed state of the rolled foamed sheet 3, the possibility exists that slight gaps may form in the contact portion of the rough surfaces which enable water to penetrate into the gaps and, in turn, the wires.
Accordingly, it is an object of the present invention to provide a water penetration prevention construction. The construction prevents gaps from forming on a contact portion of a foamed sheet during rolling of the electric wires while the electric wires are sandwiched between the foamed sheets.
To achieve the object, a foamed sheet having independent cells is provided to prevent water from penetrating between electric wires inserted into an electric wire insertion portion of a grommet.
In the construction, the foamed sheet has an adhesive layer on its upper and lower surfaces. A plurality of the electric wires are disposed at required intervals in a region whose area is approximately half of that of the adhesive layer formed on the upper surface of the foamed sheet. The foamed sheet is folded on itself to sandwich the electric wires between the adhesive layer formed on the upper surface. The folded foamed sheet is rolled to dispose a plurality of the electric wires in the foamed sheet. The adhesive layer formed on the lower surface of the foamed sheet is bonded to itself.
According to the water penetration prevention construction, in the portion of the foamed sheet where the electric wires are disposed, the adhesive layer sandwiches the electric wires. The adhesive layer is in contact with itself. Thus, the adhesive layer is capable of closely surrounding the periphery of the electric wires and adhering to itself at its boundary. Accordingly, when the foamed sheet is rolled, the lower surface of the foamed sheet that does not sandwich the electric wires therebetween contacts itself. Because the adhesive layer is also formed on the lower surface of the foamed sheet, it is possible to secure a state in which the adhesive layer adheres to itself. Accordingly the foamed sheet does not have a gap between the lower surface that contacts itself, thus ensuring water penetration prevention performance.
In another aspect of the present invention, a foamed sheet having independent cells is provided to prevent water from penetrating between electric wires inserted into an electric wire insertion portion of a grommet.
In the construction, the foamed sheet has an adhesive layer on an upper surface and a smooth film layer on a lower surface. A plurality of the electric wires are disposed at required intervals in a region that is approximately half of that of the adhesive layer formed on the upper surface of the foamed sheet. The foamed sheet is folded upon itself to sandwich the electric wires between the adhesive layer formed on the upper surface, the folded foamed sheet is rolled to dispose a plurality of the electric wires in the foamed sheet. The film layer, formed on the lower surface of the foamed sheet is in contact with itself.
More specifically, the smooth film layer can be obtained by making the foamed sheet of chloroprene rubber. According to the above-described construction, when the foamed sheet is folded and rolled, the lower surface of the foamed sheet including the smooth film layer, contacts itself. Thus the foamed sheet does not have a gap between the lower surface. This ensures a water penetration prevention effect that is similar to that of the water penetration construction having the adhesive layer. Further, during rolling of the foamed sheet, even though the smooth film layer formed on the lower surface touches the operator""s hands, the smooth film layer does not stick to the operator""s hands unlike the adhesive layer. Thus, it is possible to improve the operability during rolling of the foamed sheet.
Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.